The Mills Canyon Fire remains uncontained since breaking out on Tuesday near the tiny eastern town of Entiat, in Chelan County. More than 18,000 acres of grass, brush and timber have been burnt, according to Inciweb, a joint-agency fire information website.

"Challenges for fire personnel include steep rocky terrain, flashy fuels, and warm weather conditions," a statement on the website said.

Three outbuildings have been damaged. Residents in about 15 buildings were ordered away on Thursday afternoon, and residents in more than 200 homes were told to be on alert or ready to flee. It was unclear how many remained under evacuation orders or threatened early on Friday.

Authorities late on Thursday had re-opened a 30-mile stretch of Highway 97A they had closed earlier because of threats from thick smoke and rolling debris. Commercial orchards, a sheep herding operation, and sensitive plant life were threatened.

A media image showed towering flames licking a side of Entiat's Numeral Mountain as winds urged the blaze toward the Columbia River.

Weather was little help to the roughly 450 firefighters backed up by aircraft dumping payloads of flame retardant. Temperatures in the 90s and local wind gusts at higher elevations were forecast from Friday through the weekend.

"Conditions should remain warm and dry through at least the early part of next week," National Weather Service meteorologist Jaret Rogers said.